Conventional locking fasteners have employed serrated washers, cotter pins or the like for interlocking threaded members and preventing loosening of fastener elements during vibration, thermal variations, and the like. Such devices are useful in certain applications wherein access may be conveniently obtained to both sides of a workpiece, whereby a worker may employ tools for rotatively driving a bolt or the like from one side of the workpiece while engaging a mating, locking nut or the like adjacent the opposite side of the workpiece. In applications wherein access is available only to an outer surface area of the workpiece, however, the use of lock washers, cotter pins or locking nuts is not practicable because of the difficulty of installing the members on the inaccessible or "blind" end of the bolt.
For certain applications, it has been attempted to provide blind fasteners which may be inserted and removed from an outer surface of an aircraft panel or the like. Such blind fasteners, in the past, have been secured in position by friction or by bonding, but they suffer from several inherent limitations and disadvantages. Conventional friction fasteners, for example, which are wedged into position within a bore formed within the workpiece, are readily removable but tend gradually to shift out of position during use under vibratory loads or in high temperature environments, particularly at temperatures in excess of 1600.degree. F. Bonded or implanted fasteners are not readily removable and must often be destroyed, during removal by drilling or other destructive means. Other prior-art fastener devices have employed spring-biased locking elements. At high temperatures, however, such spring-loaded locking elements tend to relax and fail because of what is termed in the art "creep relaxation," wherein the prebiased elements tend to lose their spring bias.
Another limitation of conventional fastener devices is that their insertion and locking may themselves induce deleterious stress loads on the workpiece or panels in which they are mounted. Particularly when the fasteners are installed in structures formed of temperature resistant materials, which may tend to be more frangible than metal components, the locking action entailed in tightening the locking members tends to exert an objectionable level of stress on the workpiece, which is further aggravated by exposure to cyclical and excessively high temperatures.